Boiler



Oct. 31,

K. TOENSFELDT ET AL BOILER Filed April l5, 1937 INVENTORS ATT RNEY M J CRUJS,

Patented Oct. 31, 1939 UNITED STATES PATENT oFFicE 2,177,917 I Y, Bonini Application April 15, 1937, Serial No. 137,052

8 Claims.

The present invention relates to steam generators in whichthe water to be evaporated is forced through the ,generator by means such as a pump and ows through the generator for the main portion only once.

In some generators of this forced-circulation type the water is all evaporated and leaves the generator as steam whereas in others an excess of water is supplied and this excess leaves the generator together with the steam, the two being separated after leaving the generator.

In the former type all, or a great part, of the impurities contained in the water will be deposited at the point where the last evaporation occurs and this material must be periodically washed out or removed by other means. This requires more or less complicated and expensive apparatus and mo-reover there is always danger that during periods between washings a portion of the impurities, instead of being deposited on the generator walls, will be carried over to the superheater and turbine or other prime mover, which is objectionable. y

In those steam generators in which an `excess of water is fed to the apparatus and separated out from the steam, apparatus has to be employed, for the sake of economy, to reclaim the heat in this excess water before the excess is allowed to flow to waste. Even then there is involved the waste of water and moreover an unnecessarily large boiler feed pump is required.

If this excess were to be recirculated together with the fresh incoming feed water, it would mean that a great deal of the boiler water would have to be blown off to keep down the concentration.

The present invention, which is intended to overcome the difficulties encountered in the former arrangements briefly described above, will be described in connection with the drawing filed herewith in which there are shown diagrammatically in two figures two arrangements for carrying out the invention.

Referring rst to Fig. 1, the boiler housing is shown at I. The heating gases come from any suitable source such as the burner 2, these gases leaving for the stack (not shown) at 3 after having given up their heat. The boiler feed pump 4 feeds water to the economizer 5. At the point 6 the water leaving the economizer divides into two portions, one flowing through 'I to the drum 8 and the other flowing through pipe 9 to the circulating pump IO. Valve 9a in line 9 makes it possible to regulate the relative amounts of water flowing through 1 and 9. 'I'he circulating (Cl. D22- 459) pump delivers the water to the steam generating coils II and I2 located respectively in the upward and downward passes in the housing I formed therein by means of the partition I3. The amount of water forced into the generator by pump I0 is such that it is not all evaporated in the coils I I and I2. The mixture of steam and water from the coil I2 is delivered by means of pipe I4 to drum 8. In this drum the unevaporated water separates from the steam and the steam passes through the steam washer or deconcentrator I5, after which it passes by means of pipe I6 to the superheater I'I7 flowing thence through pipe I8 to the `point of consumption.

The portion of the water leaving the economizer 5 and passing from point 6 through line 1 to the drum 8 is used to wash the steam in the deconcentrator I5. This portion of the water together with the unevaporated excess reaching the drum through line I4 collects in the lower portion of Vdrum 8 and ows thence through pipe I9 to the settling tank 2l] in which the impurities delivered by the pipe I4 in the excess water are allowed to settle. The part of the water in the lower part of purier 20 containing the concentrated impurities is blown off periodically through pipe 2| while the purified water leaves the settling tank 2li at the top through pipe 22 and, at 23, joins the portion of the feed water coming through pipe 9 from the economizer, and flows together with it to the circulating pump I0.

It is obviously desirable to keep the amount of water treated in the settling tank 28 as small as` possible. This is the reason why the coil I2, through which the water and steam pass just before their discharge to drum 8, is placed in the last gas pass where the temperature of the gases is not as intense as it is in the iirst pass. This makes it possible to approach nearer tothe point of total evaporation without danger of burning out the tubesl at this point. 'Ihere is therefore a close connection between this location of the last part of the evaporating surface and the use of the settling tank.

The rate at which the circulating pump Ill must force Water through the steam generator bears a constant relation to the rate at which fresh water is supplied by the pump 4 and steam is taken off by the pipe I8. The two pumps 4 and I Il can therefore be, as indicated diagrammatically in the drawing,` mounted on a common shaft and driven by the common motor shown at 25. This motor is made responsive to the water level in drum 8 by any desired means, indicated at 24.

The operation of the device will be clear from the above and no further statement regarding it seems called for.

In Fig. 2 there is shown an arrangement in general similar to the one just described but avoiding the mixing of the excess water from the evaporator with fresh water. The water from the economizer 5 is all delivered through pipe 'l' into the drum 8, being there used to purify the steam in the deconcentrator l5. The excess water from the evaporator together with the steam generated is delivered from coil i2 through pipe i4 to a separating drum i0 preferably located at the same level as drum 8. Here the steam and water separate, the steam flowing through pipe 4l into drum 8 to be purified in the deconcentrator I5, and the water owing through pipe 42 to the settling tank Z. In the settling tank 2i) the impurities are allowed to settle to be blown off periodically through 2|, the purified water leaving through pipe 22 and joining the water coming from drum 8 through pipe I9. The two together then flow to the circulating pump I0. It will be seen that the amount of water delivered to the settling tank 2P) is less in this form. of the invention, being only the excess from the evaporator. The size of the settling tank can therefore be considerably smaller than in the form of the invention shown in Fig. 1.

Without departing from the spirit of the invention some variations can obviously be introduced in practice.

What we claim is:

i. In the art of steam generation and purification the method comprising the steps of forcing water through the evaporating section of a boiler at a rate in excess of the rate of steam generation, separating the steam generated from all of the unevaporated water delivered with the steam by the evaporating section of the boiler, removing impurities from the steam by means of boiler feed water, concentrating the impurities carried by said unevaporated water in a small portion thereof, wasting said small portion, and using the remaining puried portion of the unevaporated water together with the feed water that has been used to purify the steam as water to be forced through the evaporating section.

2. In the art of Steam generation and purincation the method comprising the steps of forcing water through the evaporating section of a boiler at a rate in excess of the rate of steam generation, separating the steam generated from all of the unevaporated water delivered with the steam by the evaporating section of the boiler, removing impurities from the steam by means of boiler feed water, concentrating the impurities carried by said unevaporated water in a small portion thereof, wasting said small portion, adding the purified remaining portion of the unevaporated water to the feed water that has been used to remove impurities from the steam and using the mixture as water to be forced through the evaporating section.

3. In the art of steam generation and purification the method comprising the steps of forcing water through the evaporating section of a boiler at a rate in excess of the rate of steam generation, separating the steam from all of the unevaporated water delivered with the steam by the evaporating section of the boiler, removing impurities from the steam by means of a portion only of the boiler feed water, concentrating the impurities carried by said unevaporated water in a small portion thereof, wasting said small portion, and using the remaining purified portion of the unevaporated water together with the portion of the feed water that has been used to purify the steam and the portion that has not been so used as water to be forced through the evaporating section.

4. In the art of steam generation and purification the method comprising the steps of forcing water through the evaporating section of a boiler at a rate in excess of the rate of the steam generation, separating the steam generated from all of the unevaporated water delivered with the steam by the evaporating section of the boiler, removing impurities from the steam by means of a portion only of the boiler feed water, mingling the separated unevaporated water with the portion of the feed water used for purifying the steam, concentrating the impurities in the water after purifying the steam in a small portion thereof, wasting said small portion, and using the remainder together with the portion of the feed water that has not been used to purify the steam as water to be forced through the evaporating section.

5. In apparatus of the class described, the combination of a once-through iiow steam generating section, means to force water through said section at a rate in excess of the rate of steam generation, a chamber to which the steam and water mixture from the steam generating section is led and where the two are separated, means for conducting the steam and water mixture from said generating section to said chamber, means for purifying the steam by means of feed water on its way to the steam generating section, means including a chamber for concentrating the impurities in said separated unevaporated water in a small portion thereof, means for conducting the separated unevaporated water to said second chamber, means for wasting said small portion, and means to lead the remaining part of the unevaporated water and the feed water that has been used to purify the steam to said first named means.

6. In apparatus of the class described, the combination of a once-through flow steam generating section, a pump adapted and arranged to force water through said section at a rate in excess of the rate of Steam generation, a chamber to which the steam and water mixture from the said section is delivered and where the two are separated, means for conducting the steam and water mixture from said generating section to said chamber, a second chamber, means to deliver the separated steam and at least a portion of the feed water to it, means within the second chamber for purifying the steam by means of such feed water, a third chamber to which the excess of water is carried after said separation, means for conducting said excess of water from said first chamber to said third chamber, means within said third chamber for concentrating the impurities in said separated excess in a small portion thereof, means to waste said small portion, and connections to carry the remaining part of the excess and the feed water which has been used in said second chamber for purifying the steam to the pump.

'7. In the art of steam generation and purification the method comprising the steps of forcing water through the evaporating section of a boiler at a rate in excess of the rate of steam generation, the last part of the evaporating being done entirely by convection heat from gases that have left the furnace, separating the steam generated from all of the unevaporated water delivered with the steam by the evaporating section of the boiler, removing impurities from the steam by means of boiler feed Water, concentrating the impurities carried by said separated evaporated Water in a small portion thereof, Wasting said small portion, and using the remaining portion of the unevaporated water together with the feed Water that has been used to purify the steam as Water to be forced through the evaporating section.

8. In apparatus of the class described, the combination of a boiler housing comprising a pass through which the gases flow after they have left the furnace and `in which substantially all heating is done by convection, a once-through steam generating section arranged with the part adjacent to its outlet located in said pass, means to force water through said section at a rate in excess of the rate of steam generation, a chamber to which the steam' and water mixture from the steam generating section is led and Where the two are separated,` means for conducting the steam and water mixture from said generating section to said chamber, means for purifyingthe steam by means of feed Water on its Way to the steam generating section, means for concentrating the impurities in said separated excess in a small portion thereof, means for Wasting said small portion, and means to lead the remaining part of the excess and the feed water that has been used to purify the steam to said first named means.

KURT TOENSFELDT. BERTRAM J.. CROSS. 

